Blends of ethylenic polymers with improved modulus and melt strength and articles fabricated from these blends

ABSTRACT

A blend which comprises;  
     A) a heterogeneous or homogenous linear ethylene homopolymer or interpolymer;  
     B) a branched homopolymer or interpolymer;  
     wherein said blend has;  
     1) a melt index, I2, of about 0.05 to about 20 g/10 min;  
     2) a flexural modulus of ≧100,000 psi or ≦30,000 psi;  
     3) a melt strength of ≧2 cN;  
     4) a melt extensibility of ≧25 mm/sec; and  
     5) wherein said melt strength of said blend meets the following relationship;  
     Melt strength≧ F   MS * [( f*A )+((1− f )* B )]; where:  
     A=3.3814*(I2) −0.6476  and B=16.882*(I2) −0.6564 ; where  
     I2 is the measured melt index of the blend; f is the weight fraction of the linear polyethylene in the blend and F MS  is ≧1.1.  
     Also included in the present invention are foams, films, fibers, blow molded articles, wire and cable articles and extrusion coatings comprising said blend.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/274,789, filed Mar. 9, 2001, the entire contents ofwhich are herein incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable

FIELD OF THE INVENTION

[0003] This invention describes resin formulations having a flexuralmodulus of greater than or equal to 100,000 psi or less than or equal to30,000 psi, which also yield previously inaccessible high melt strengthsat a given melt index. This invention also provides fabricated articlesincluding foams made from these resin formulations.

BACKGROUND OF THE INVENTION

[0004] Blends of low density polyethylene (LDPE) and linear low densitypolyethylene (LLDPE) are known in the prior art. For example, Ghijselset al., in “Melt Strength Behavior of Polyethylene Blends”, Intern.Polymer Processing VII (1992), p. 44-50, exemplifies blends of LDPE andLLDPE, where the LLDPE has a melt index (I2) of 0.1 g/10 min and thefinal blend densities are approximately 0.92 g/cm³, and which show asynergistic improvement in melt strength. A polyethylene resin densityof 0.92 g/cc corresponds approximately to a flexural modulus of 40,000psi. However, Ghijsels neither exemplifies nor gives any indication ofthe range of the ethylenic blend components in which synergy would beobserved for blends having a flexural modulus greater than or equal to100,000 psi, nor less than or equal to 30,000 psi.

[0005] U.S. Pat. Nos. 5,863,665 and 5,582,923 describe an ethylenepolymer extrusion composition comprising from about 75 to 95 percent ofat least one ethylene/α-olefin interpolymer composition selected fromthe group consisting of a substantially linear ethylene polymercomposition, a homogeneously branched linear ethylene polymercomposition and a heterogeneously branched linear ethylene polymercomposition, (wherein the ethylene/α-olefin polymer is characterized ashaving a density in the range of 0.85 g/cc to 0.940 g/cc) and from about5 to 25 percent of at least one high pressure ethylene polymercharacterized as having a melt index, I2, of less than 6.0 g/10 minutes,a density of at least 0.916 g/cc, a melt strength of at least 9 cN asdetermined using a Gottfert Rheotens unit at 190° C., a Mw/Mn ratio ofat least 7.0 and a bimodal molecular weight distribution as determinedby gel permeation chromatography, wherein the ethylene polymer extrusioncomposition has a melt index, I2, of at least 1.0 g/10 minutes. Theblends of this composition would have flexural modulus less than about115,000 psi. In contrast, the blends of the present invention would haveflexural modulus ≧120,000 psi at comparable melt strength. Furthermore,this patent does not teach, exemplify or claim foams.

[0006] U.S. Pat. No. 4,649,001 describes a process for producing apolyethylene extruded foam, which comprises melting and kneading acomposition of a polyethylene-based resin containing a foaming agentfollowed by extrusion-foaming. A linear low-density polyethylene havinga broad molecular weight distribution is used as the polyethylene-basedresin. The linear low-density polyethylene used has a density of 0.920to 0.940 g/cm³, a melt flow rate of 0.3 to 10 g/10 min and arelationship between a weight average molecular weight and a numberaverage molecular weight (Mw/Mn) greater than or equal to 4. Low densitypolyethylene of 0.918 to 0.923 g/cm³ density may also be blended to makefoams. The foams were all extruded. Cross-linked foams were not claimed.The highest flexural modulus of the resins used to make the extrudedfoams would correspond to about 120,000 psi (at a resin density of 0.940g/cm³), but this would not be a blend. Furthermore, the density of thelinear low-density polyethylene was 0.940 g/cm³ or less.

[0007] U.S. Pat. No. 4,226,946 discloses polyethylene blend foams havingdensity from about 3.0 to about 15.0 pounds per cubic foot,substantially closed-cell structure and average compressive strength at10 percent deformation of from about 7 to about 170 psi, preferablyabout 7 to about 60 psi, and an improved method and a means for makingthe same from polyethylene blends and at least one blowing agent usinggel-forming extrusion technology. The polyethylene blend comprises fromabout 35 to about 60 weight percent of low density branched polyethylene(0.910 to 0.930 g/cc density) in admixture with from about 40 to about65 weight percent of intermediate density linear polyethylene (0.931 to0.940 g/cc density). The densities of the resulting blends would be lessthan 0.9365 g/cc (corresponding to a flexural modulus less than about100,000 psi) and greater than 0.9180 g/cc (corresponding to a flexuralmodulus greater than about 40,000 psi).

[0008] However, there is still a need for resin compositions which,while achieving a required flexural modulus ≧100,000 psi or ≦30,000 psi,can also exhibit high melt strength and/or melt extensibility, at agiven melt index. We have surprisingly found that certain compositionsexhibit synergistic improvements in melt strength and, in some cases,even more surprisingly, in melt extensibility at this melt strength.Branched resins can't achieve the modulus possible with linearpolyethylene resins, and linear resins would have to have much lowermelt index than branched resins of comparable melt strength.Furthermore, the melt strength achieved with the blends used in thepresent invention may exceed, at a given melt index, the melt strengthachievable with any branched resin or linear resin at the same meltindex and/or density. Consequently, the blends used in the presentinvention exhibit greatly improved melt strength compared with a linearpolyethylene resin of the same density.

[0009] The extrusion foam manufacturing process requires a resin ofsufficiently high melt strength to allow the bubble structure tomaintain its integrity during the expansion process immediately afterextrusion from the die. Prior to this invention, the only resins capableof meeting this requirement at the melt index suitable for processing(I2>0.5, preferably >1 g/10 min) were branched resins such as LDPE, EVAand the like. Hence, the flexural modulus was limited to that obtainablewith these branched resins (i.e. about 80,000 psi or less, equivalent toan LDPE of density less than or equal to approximately 0.930 g/cm³). Itwould be highly desirable to produce a foam using resin of highermodulus (>100,000 psi), as this allows the overall density of the foamto be reduced, while maintaining the compressive strength of higherdensity foam made from a branched resin (although this resin has thelimitation of lower modulus).

[0010] The present invention describes blends comprising branched resins(eg LDPE) and linear resins (eg LLDPE prepared by for example Zieglerand/or metallocene catalysts). These blends provide a unique combinationof increased melt strength and modulus at a given melt index, I2.Optionally, specific blend formulations may also be selected to providemodulus both higher or lower than that achievable with LDPE alone. Thusthis invention can provide blends of flexural modulus greater than orequal to 100,000 psi or less than 30,000 psi, at melt strengths similarto or greater than those associated with LDPE or linear polyethylenehaving similar melt index, I2.

[0011] The blends of the present invention are useful for fabricatinghigh modulus foams, the preparation of which requires high meltstrength. The resulting high modulus compositions (i.e., greater than100,000 psi flexural modulus) are particularly suitable for manufactureof crosslinked and noncrosslinked foams. Thus the foams of the presentinvention have compressive strength and load bearing capacity similar tothat of foams made from branched polyethylenes, but the inventive foamshave significantly lower foam density (allowing a significant reductionin the amount of resin, by weight, necessary to produce such foams). Inaddition, the upper service temperature of the foams of this inventionmay also be improved, resulting in subsequent improvement in foamdimensional stability. No resin with this combination of properties iscurrently available.

[0012] The high modulus foams of the present invention comprise blendsof high melt strength branched resin of relatively low modulus, withlinear resin of higher density and therefore higher modulus, to yield afinal blended resin of modulus greater than 100,000 psi. Commerciallyavailable branched ethylenic resins cannot achieve this modulus.

[0013] Also included in the present invention are so called “soft”foams. These foams comprise blends of high melt strength branched resinof relatively low modulus, with linear resin of lower density andtherefore lower modulus, to yield a final blended resin of flexuralmodulus less than or equal to 30,000 psi. Commercially available lowdensity polyethylene cannot achieve this modulus either. Ethyleniccopolymers such as ethylene vinyl acetate (EVA) and ethylene acrylicacid (EAA) can have flexural modulus less than 30,000 psi, but theseresins are not thermally stable at high temperatures (i.e., degradereadily) and often result in significant discolouration and/or smell.Thus, these resins only have limited utility for extruded,non-crosslinked foams.

BRIEF SUMMARY OF THE INVENTION

[0014] A blend which comprises;

[0015] A) a heterogeneous or homogenous linear ethylene homopolymer orinterpolymer;

[0016] B) a branched homopolymer or interpolymer;

[0017] wherein said blend has;

[0018] 1) a melt index, I2, of about 0.05 to about 20 g/10 min;

[0019] 2) a flexural modulus of ≧100,000 psi or ≦30,000 psi;

[0020] 3) a melt strength of ≧2 cN;

[0021] 4) a melt extensibility of ≧25 mm/sec; and

[0022] 5) wherein said melt strength of said blend meets the followingrelationship;

Melt strength≧F _(MS)*[(f*A)+((1−f)*B)]; where:

[0023] A=3.3814*(I2)^(−0.6476) and B=16.882*(I2)^(−0.6564); where

[0024] I2 is the measured melt index of the blend; f is the weightfraction of the linear polyethylene in the blend and FMS is ≧1.1.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Definitions

[0026] All references herein to elements or metals belonging to acertain Group refer to the Periodic Table of the Elements published andcopyrighted by CRC Press, Inc., 1989. Also any reference to the Group orGroups shall be to the Group or Groups as reflected in this PeriodicTable of the Elements using the IUPAC system for numbering groups.

[0027] Any numerical values recited herein include all values from thelower value to the upper value in increments of one unit provided thatthere is a separation of at least 2 units between any lower value andany higher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to 90,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which are lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

[0028] The term “hydrocarbyl” as employed herein means any aliphatic,cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substitutedcycloaliphatic, aliphatic substituted aromatic, or aliphatic substitutedcycloaliphatic groups.

[0029] The term “hydrocarbyloxy” means a hydrocarbyl group having anoxygen linkage between it and the carbon atom to which it is attached.

[0030] The term “interpolymer” is used herein to indicate a polymerwherein at least two different monomers are polymerized to make theinterpolymer. This includes copolymers, terpolymers, etc.

[0031] The term “soft foam” is used herein to indicate a foam which hasan Asker C hardness less than about 30, preferably less than about 25and most preferably less than about 20. The hardness of the presentfoams was measured using an Asker C durometer for cellular rubber andyarn in accordance with ASTM D2240-97 (but with a spherical indentor ofabout 5 mm diameter).

[0032] Melt Index (I2, g/10 min) was determined by ASTM D-1238 (190°C./2.16 kg).

[0033] Density (g/cm³) was determined by ASTM D-792.

[0034] Elexural Modulus was measured in accordance with ASTM D-790,Method 1. A bar of rectangular cross-section was tested using athree-point loading system and a 10 pound load cell.

[0035] Melt Tension

[0036] The melt tension (in grams) was measured at 190° C. using a 2.16kg load and pulling strands of molten polymers at 50 rpm around a pulleysystem for a haul-off rate over a thirty second period. The melt tensionwas the average force over this period.

[0037] Melt Strength (MS, Measured in cN) and Melt Extensibility (ME,Measured in mm/s)

[0038] The measurements were conducted by pulling strands of the moltenpolymers or blends at constant acceleration until breakage occurred. Theexperimental set-up consisted of a capillary rheometer and a Rheotensapparatus as take-up device. The force required to uniaxially extend thestrands was recorded as a function of the take-up velocity. The maximumforce attained before either draw resonance or breakage occurred wasdefined as the melt strength. The velocity at which draw resonance orbreakage occurred was defined as the melt extensibility. Draw resonance,which terminated in breakage, was indicated by the onset of a periodicoscillation of increasing amplitude in the measured force profile. Inthe absence of any observable draw resonance, the melt strength wasdefined as the force at break. These tests were run under the followingconditions: Mass flow rate 1.35 gram/min Temperature 190° C. Capillarylength 41.9 mm Capillary diameter 2.1 mm Piston diameter 9.54 mm Pistonvelocity 0.423 mm/s Shear rate 33.0 s⁻¹ Draw-down distance 100 mm (dieexit to take-up wheels) Cooling conditions ambient air Acceleration 2.4mm/s²

[0039] Upper Service Temperature (UST)

[0040] A thermomechanical analyzer (TMA) commercially available fromPerkin Elmer Corporation under the trade designation model TMA 7 wasused to measure the upper service temperature (UST) of the polymers andblends. Probe force of 102 g and heating rate of 5° C./min were used.Each test specimen was a disk with thickness of 3.3 mm and 7.8 mmdiameter, prepared by compression molding at 205° C. and air-cooling toroom temperature. The temperature at the probe penetration of 1 mm wastaken as the upper service temperature (UST).

[0041] The Blend Compositions.

[0042] The blend compositions of the present invention comprise one ormore linear homopolymers or interpolymers (Component A) and one or morebranched homopolymers or interpolymers (Component B).

[0043] Component A

[0044] The linear homopolymers and interpolymers comprising Component A,are those prepared using so called coordination catalysis includingZiegler and metallocene type catalyst systems. The linear interpolymerscan be further divided into homogeneous or heterogeneous polymers,depending upon how the comonomer is distributed within the interpolymermolecules.

[0045] The linear homogeneous polymers and interpolymers used asComponent A in the blends of the present invention are herein defined asdefined in U.S. Pat. No. 3,645,992 (Elston), the disclosure of which isincorporated herein by reference. Accordingly, homogeneous polymers andinterpolymers are those in which the comonomer is randomly distributedwithin a given interpolymer molecule and wherein substantially all ofthe interpolymer molecules have the same ethylene/comonomer ratio withinthat interpolymer. The homogeneous polymers have a narrow compositiondistribution.

[0046] The term “narrow composition distribution” used herein describesthe comonomer distribution for homogeneous interpolymers and means thatthe homogeneous interpolymers have only a single melting peak andessentially lack a measurable “linear” polymer fraction. The narrowcomposition distribution homogeneous interpolymers can also becharacterized by their SCBDI (short chain branch distribution index) orCDBI (composition distribution branch index). The SCBDI or CBDI isdefined as the weight percent of the polymer molecules having acomonomer content within 50 percent of the median total molar comonomercontent.

[0047] The CDBI of a polymer is readily calculated from data obtainedfrom techniques known in the art, such as, for example, temperaturerising elution fractionation (abbreviated herein as “TREF”) asdescribed, for example, in Wild et al, Journal Of Polymer Science, Poly.Phys. Ed., Vol. 20, p. 441 (1982), or in U.S. Pat. No. 4,798,081, andU.S. Pat. No. 5,008,204 and WO 93/04486, the disclosures of all of whichare incorporated herein by reference. The SCBDI or CDBI for the narrowcomposition distribution homogeneous interpolymers and copolymers of thepresent invention is preferably greater than about 30 percent,especially greater than about 50 percent. The narrow compositiondistribution homogeneous interpolymers and copolymers used in thisinvention essentially lack a measurable “high density” (i.e.,homopolymer) fraction as measured by the TREF technique. The linearhomogeneous interpolymers and polymers also have a degree of branchingless than or equal to 2 methyls/1000 carbons in about 15 percent (byweight) or less, preferably less than about 10 percent (by weight), andespecially less than about 5 percent (by weight).

[0048] Useful linear homogeneous homopolymers or interpolymers alsoinclude the so-called substantially linear polymers defined as in U.S.Pat. No. 5,272,236 (Lai et al.), and in U.S. Pat. No. 5,278,272, theentire contents of which are incorporated by reference.

[0049] Linear heterogeneous homopolymers and interpolymers can also beused as Component A in the blends of the present invention.Heterogeneous interpolymers are those in which substantially all of theinterpolymer molecules do not have the same ethylene/comonomer ratio andhave a broad composition distribution.

[0050] The term “broad composition distribution” used herein describesthe comonomer distribution for heterogeneous interpolymers and meansthat the heterogeneous interpolymers have a “linear” fraction and thatthe heterogeneous interpolymers have multiple melting peaks (i.e.,exhibit at least two distinct melting peaks). The linear heterogeneousinterpolymers and polymers also have a degree of branching less than orequal to 2 methyls/1000 carbons in about 10 percent (by weight) or more,preferably more than about 15 percent (by weight), and especially morethan about 20 percent (by weight). The heterogeneous interpolymers alsohave a degree of branching equal to or greater than 25 methyls/1000carbons in about 25 percent or less (by weight), preferably less thanabout 15 percent (by weight), and especially less than about 10 percent(by weight) of the total polymer.

[0051] The linear homogeneous and heterogeneous polymers andinterpolymers used to make the novel polymer compositions used in thepresent invention can be ethylene homopolymers or interpolymers ofethylene with at least one C₃-C₂₀ α-olefin. Preferred monomers includeethylene, 1-propene, 1-butene, 1-hexene, 4-methyl-1-pentene, and1-octene. Other preferred monomers include styrene, halo- or alkylsubstituted styrenes, vinylbenzocyclobutane, 1,4-hexadiene,cyclopentene, cyclohexene and cyclooctene.

[0052] Component B

[0053] The branched polymers and interpolymers used as Component B inthe blends of the present invention are defined herein as those that arepartly or entirely homopolymerized or interpolymerized in autoclave ortubular reactors at pressures above 14,500 psi (100 MPa) with the use offree-radical initiators.

[0054] Such branched polymers and interpolymers, include, but are notlimited to, low density ethylene polymers such as high pressure lowdensity ethylene homopolymer (LPDE), ethylene-vinyl acetate copolymer(EVA), ethylene-acrylic acid copolymer (EAA), ethylene-carboxylic acidcopolymers and ethylene acrylate copolymers as well as olefin polymersproduced at low to medium pressures such as polybutylene (PB).

[0055] Suitable high pressure ethylene interpolymers include ethyleneinterpolymerized with at least one, α,β-ethylenically unsaturatedcomonomers (for example, acrylic acid, methacrylic acid and vinylacetate) as described by McKinney et al. in U.S. Pat. No. 4,599,392.Preferred high pressure ethylene interpolymers comprise from 0.1 to 55total weight percent comonomer, and more preferably from 1 to 35 totalweight percent comonomer, and most preferably from 2 to 28 total weightpercent comonomer, and can be chemically and/or physically modified byany known technique such as, for example, by ionomerization andextrusion grafting.

[0056] Properties of the Blend Compositions of the Present Invention.

[0057] The blends of the present invention may be prepared by anysuitable means known in the art such as, for example, dry blending in apelletized form in desired proportions followed by melt blending in anapparatus such as a screw extruder or a Banbury mixer. Dry blendedpellets may be directly melt processed into a final solid state articleby, for example, extrusion or injection molding. The blends may also bemade by direct polymerization without isolating blend components. Directpolymerization may use, for example, one or more catalysts in a singlereactor or two or more reactors in series or parallel and vary at leastone of operating conditions, monomer mixtures and catalyst choice.Blending the branched and linear resins at melt temperatures greaterthan 230° C. may lead to a further increase in melt strength.

[0058] We have found, unexpectedly, that by blending certain branchedpolyethylene resins with higher density linear polyethylene resins, weobtain a resin blend of a certain melt index range with the necessarymelt strength to permit foam production. This melt strength issynergistically much higher than that expected from a linear combinationof the two components.

[0059] The melt strength of the blend meets the following relationship;

Melt strength≧F _(MS)*[(f*A)+((1−f)*B)] where:

[0060] A=3.3814*(I2)^(−0.6476) and

[0061] B=16.882*(I2)^(−0.6564)

[0062] Where I2 is the measured melt index of the blend; f is the weightfraction of the linear polyethylene (Component A) in the blend.

[0063] F_(MS) is a measure of synergy in melt strength in a blend. WhenF_(MS)=1.0, the blend exhibits no synergistic improvement in meltstrength with respect to the melt index of the blend. It is oftenobserved that the blend melt index is unexpectedly low, which in itselfleads to unexpectedly high melt strength. Thus the definition of synergyherein is very conservative and F_(MS)>1 always indicates a substantiallevel of synergy and unexpectedly high melt strength. When F_(MS)>1, theblend is synergistic in that it shows greater melt strength thanexpected (or predicted) from a combination of linear and branchedethylenic polymers at the melt index of the blend.

[0064] For the blends of the present invention, FMS is ≧1.1, preferably≧1.25, more preferably ≧1.5, even more preferably ≧2.0, most preferably≧2.5.

[0065] The final melt index, I2, of the blend composition is from about0.05 to about 20, preferably from about 0.1 to about 10, more preferablyfrom about 0.2 to about 7, even more preferably 0.5 to 5 g/10 min.

[0066] The final melt strength of the blend composition is greater thanor equal to 2 cN, more preferably greater than or equal to 7 cN, mostpreferably greater than or equal to 10 cN.

[0067] The final melt extensibility of the blend composition is greaterthan or equal to 25, preferably greater than or equal to 50, mostpreferably greater than or equal to 75 mm/sec.

[0068] The final flexural modulus of the blend composition is greaterthan or equal to 100,000 psi, more preferably greater than or equal to120,000 psi and, most preferably greater than or equal to 130,000 psi.

[0069] In another embodiment, the final flexural modulus of the blendcomposition is less than or equal to 30,000 psi, preferably less than orequal to 25,000 psi and most preferably less than or equal to 20,000psi.

[0070] For the blends with flexural modulus greater than or equal to100,000 psi, the upper service temperature (UST) of the blends will begreater than about 115° C., preferably greater than about 118° C., morepreferably greater than about 121° C. and even more preferably greaterthan about 125° C.

[0071] The melt index, I2, of Component A, is less than about 60 g/10min, preferably less than about 30 g/10 min, more preferably less thanabout 15 g/10 min and most preferably less than about 10 g/10 min.

[0072] Suitable branched ethylenic polymers, Component B, include EVA,LDPE and EAA of melt index of 0.05-10 g/10 min. It is most preferable touse LDPE. For the blends with flexural modulus greater than or equal to100,000 psi, Component A, should have a modulus greater than about138,000 psi, preferably greater than about 164,000 psi, and morepreferably greater than about 210,000 psi. It is most preferred thatComponent A be an ethylene homopolymer.

[0073] For the blends with flexural modulus less than or equal to 30,000psi, Component A should have a modulus less than about 28,000 psi,preferably less than about 25,000 psi, more preferably less than about22,000 psi.

[0074] The blends of the present invention may optionally comprise“additional polymers” including one or more other thermoplastics toprovide additional improvements in properties including but not limitedto processability, upper service temperature, modulus, compressivestrength, hardness, toughness, increased foam cell size, and aestheticsof the final foams or articles fabricated therefrom. Examples of the“additional polymers” include, but are not limited to, low densitypolyethylene (LDPE), high density polyethylene (HDPE), linear lowdensity polyethylene (LLDPE), ethylene styrene interpolymers (ESI),polypropylene (PP), polystyrene (PS), ethylene-propylene rubber andstyrene-butadiene rubber. In one embodiment, the blends of the presentinvention may be further blended with alkenyl aromatic polymers (such aspolystyrene) to make, for example, alkenyl aromatic polymer foams withincreased cell size.

[0075] Applications of these blends include those in which meltstrength, modulus and/or upper service temperature are key performancerequirements, for example, non-crosslinked foams for cushion packaging,sports and leisure, building and construction, etc; non-crosslinkedblowmolded articles; crosslinked foams for applications such asautomotive; non-crosslinked foam bottle labels; films; fibers; wire andcable; and extrusion coatings.

[0076] The Foams of the Present Invention.

[0077] The present invention provides blends with flexural modulus aboveabout 100,000 psi simultaneously with high melt strength and high meltextensibility at comparatively higher melt indices, therefore broadeningthe applicability of high modulus resins into foam structures andprocesses not previously attainable or viable with traditional linear orsubstantially linear polyethylene. It is not possible to achieve theseMS, ME and MI combinations using linear polymers of flexural modulus of100,000 psi or more. With a branched ethylenic polymer, it is possibleto achieve the MS and ME but the flexural modulus will be 80,000 psi orless.

[0078] The present invention also provides blends with flexural modulusless than about 30,000 psi simultaneously with high melt strength andhigh melt extensibility at comparatively higher melt indices, thereforebroadening the applicability of low modulus resins into foam structuresand processes not previously attainable or viable with traditionallinear polyethylene. It is not possible to achieve these melt strength,high melt extensibility and melt index combinations using linearpolymers of flexural modulus of 30,000 psi or less. With a branchedethylenic polymer other than EVA, it is not possible to achieve the MSand ME and the flexural modulus will be greater than 30,000 psi. In thecase of EVA such benefits only come with unacceptable additionalproperties such thermal instability, and odor.

[0079] The flexural modulus of these blends is higher than previouslydescribed in the prior art, giving greater stiffness and thereforegreater compressive strength than existing compositions, yet with therequired melt strength and melt extensibility to allow satisfactoryfabrication into foams. The reduced amount of resin required in thesefoams results in economic and environmental advantages over currenttechnology. At any given melt index, no previously describedpolyethylene provides the combination of melt strength, extensibilityand modulus above about 100,000 psi as described in this invention.

[0080] To prepare commercially acceptable foams of any modulus, oneneeds to have a minimum melt strength of about 2 cN, preferably greaterthan about 7 cN and most preferably greater than 10 cN, and a minimumextensibility of about 25 mm/sec, preferably greater than about 50 mm/sand most preferably greater than about 75 mm/s. LDPE resins exhibitthese properties but cannot yield the required modulus (greater thanabout 100,000 psi or alternatively less than 30,000 psi) or stiffness.HDPE or LLDPE resins can only achieve the required melt strength at amelt index (I2)<3 g/10 min, often <1 g/10 min. This causes difficultiesin foam processability, for instance, due to excessive shear heating.

[0081] This very high melt strength is a necessary requirement forsuccessful foam production and is greater than that required of branchedresins such as LDPE, and is not attainable at the same melt index anddensity with previously known branched polyethylenes. This isparticularly true for the high modulus foams of the present invention, aresult of the higher foaming temperature necessary due to the increasedmelting point of the higher density resin, and the increased amount ofblowing agent required to create the lower density foam product, both ofwhich tend to reduce the viscosity of the extrudate. Without the highmelt strength, the foam would collapse due to collapse of the foam cellstructure prior to solidification.

[0082] The foams will comprise 0.05 to 100, preferably 0.1 to 100 andmost preferably 0.2 to 100 weight percent of the blend of Components Aand B (based on total amount of polymers present in the foam).

[0083] The polymer compositions described above may be converted to foamproducts using physical and/or chemical blowing agents and anyconventional process. Foam products include, for example, extrudedthermoplastic polymer foam, extruded polymer strand foam, expandablethermoplastic foam beads, expanded thermoplastic foam beads or expandedand fused thermoplastic foam beads, and various types of crosslinkedfoams. The foam products may take any known physical configuration, suchas sheet, round, strand geometry, rod, film, solid plank, laminatedplank, coalesced strand plank, profiles and bun stock. The foam productsmay be converted into fabricated articles using any conventional processor method. For example, any one or more of expansion, coalescing andwelding may be used in making such articles, especially from expandablefoam beads. One may also mold expandable beads into any knownconfiguration that employs foam products, including, but not limited tothe foregoing configurations.

[0084] Foam forming steps of the process are known in the art. Forinstance as exemplified by the teachings to processes for makingethylenic polymer foam structures and processing them in C. P. Park.“Polyolefin Foam”, Chapter 9, Handbook of Polymer Foams and Technology,edited by D. Klempner and K. C. Frisch, Hanser Publishers, Munich,Vienna, New York, Barcelona (1991), which is incorporated here in byreference.

[0085] Foams of the present invention may be substantiallynoncrosslinked. That is, the foam structure contains 50 or less,preferably 40 or less, more preferably 30 or less, even more preferably20 or less, most preferably 10 or less weight percent gel based upon thetotal weight of foam or polymer, as measured according to ASTMD-2765-84, Method A.

[0086] Alternatively, the polymer compositions could be used to makefoams which are substantially cross-linked (that is, contain greaterthan 50 weight percent gel based upon the total weight of foam orpolymer, as measured according to ASTM D-2765-84 Method A) by furtheraddition of any known cross-linking agent. The various crosslinkingagents and technologies are described in the art. Cross-linking may beinduced by addition of a cross-linking agent. Induction of cross-linkingand exposure to an elevated temperature to effect foaming or expansionmay occur simultaneously or sequentially. If a chemical cross-linkingagent is used, it is incorporated into the polymer material in the samemanner as the chemical blowing agent. Further, if a chemicalcross-linking agent is used, the foamable melt polymer material isheated or exposed to a temperature of preferably less than 150° C. toprevent decomposition of the cross-linking agent or the blowing agentand to prevent premature cross-linking. If radiation cross-linking isused, the foamable melt polymer material is heated or exposed to atemperature of preferably less than 160° C. to prevent decomposition ofthe blowing agent. The foamable melt polymer material is extruded orconveyed through a die of desired shape to form a foamable structure.The foamable structure is then cross-linked and expanded at an elevatedor high temperature (typically, 150° C.-250° C.) such as in an oven toform a foam structure. If radiation cross-linking is used, the foamablestructure is irradiated to cross-link the polymer material, which isthen expanded at the elevated temperature as described above. Thepresent structure can advantageously be made in sheet or thin plank formaccording to the above process using either cross-linking agents orradiation.

[0087] The term “cross-linking agent” as used herein means a compound ormixture of compounds used for the purposes of substantially crosslinkinga polymer or polymer blend. The cross-linking agent used to prepare thefoams and articles of the present invention include, but are not limitedto peroxides, silanes, radiation, azides, phenols, aldehyde-aminereaction products, substituted ureas, substituted guanidines,substituted xanthates, substituted dithiocarbamates, sulfur-containingcompounds, thiazoles, imidazoles, sulfenamides, thiuramidisulfides,paraquinonedioxime, dibenzoparaquinonedioxime, sulfur; and combinationsthereof.

[0088] The various crosslinking technologies are described in U.S. Pat.Nos. 5,869,591 and 5,977,271, the entire contents of both of which areherein incorporated by reference. Dual cure systems, which use acombination of heat, moisture cure, and radiation steps, may beeffectively employed. Dual cure systems are disclosed and claimed inU.S. Pat. No. 6,124,370, incorporated herein by reference. For instance,it may be desirable to employ peroxide coupling agents in conjunctionwith silane coupling agents, peroxide coupling agents in conjunctionwith radiation, sulfur-containing coupling agents in conjunction withsilane coupling agents, etc.

[0089] The foam structures of the present invention are optionally madeby a conventional extrusion foaming process. The structure isadvantageously prepared by heating the polymer or blend to form aplasticized or melt polymer material, incorporating therein a blowingagent to form a foamable gel, and extruding the gel through a die toform the foam product. Depending upon the die (with an appropriatenumber of apertures) and operating conditions, the product may vary froman extruded foam plank or rod through a coalesced foam strand product,to foam beads and eventually to chopped strands of foamable beads. Priorto mixing with the blowing agent, the polymer material is heated to atemperature at or above its glass transition temperature or meltingpoint. The blowing agent is optionally incorporated or mixed into themelt polymer material by any means known in the art such as with anextruder, mixer, blender, or the like. The blowing agent is mixed withthe melt polymer material at an elevated pressure sufficient to preventsubstantial expansion of the melt polymer material and to advantageouslydisperse the blowing agent homogeneously therein. Optionally, anucleator is optionally blended in the polymer melt or dry blended withthe polymer material prior to plasticizing or melting. Prior toextruding foamable gel through the die, one typically cools the gel toan optimum temperature. The foamable gel is typically cooled to a lowertemperature to optimize physical characteristics of the foam structure.This temperature, often referred to as the foaming temperature, istypically above each component's polymer glass transition temperature(T_(g)), or for those having sufficient crystallinity, near the peakcrystalline melting temperature (T_(m)). “Near” means at, above, orbelow and largely depends upon where stable foam exists. The temperaturedesirably falls within 30° centigrade (° C.) above or below the T_(m).For foams of the present invention, an optimum foaming temperature is ina range in which the foam does not collapse. The gel may be cooled inthe extruder or other mixing device or in separate coolers. The gel isthen extruded or conveyed through a die of desired shape to a zone ofreduced or lower pressure to form the foam structure. The zone of lowerpressure is at a pressure lower than that in which the foamable gel ismaintained prior to extrusion through the die. The lower pressure isoptionally superatmospheric or subatmospheric (vacuum), but ispreferably at an atmospheric level.

[0090] In another embodiment, the resulting foam structure is optionallyformed in a coalesced strand form by extrusion of the polymer materialthrough a multi-orifice die. The orifices are arranged so that contactbetween adjacent streams of the molten extrudate occurs during thefoaming process and the contacting surfaces adhere to one another withsufficient adhesion to result in a unitary foam structure. The streamsof molten extrudate exiting the die take the form of strands orprofiles, which desirably foam, coalesce, and adhere to one another toform a unitary structure. Desirably, the coalesced individual strands orprofiles should remain adhered in a unitary structure to prevent stranddelamination under stresses encountered in preparing, shaping, and usingthe foam. Apparatuses and method for producing foam structures incoalesced strand form are seen in U.S. Pat. Nos. 3,573,152 and4,824,720.

[0091] Alternatively, the resulting foam structure is convenientlyformed by an accumulating extrusion process and apparatus as seen inU.S. Pat. No. 4,323,528 and U.S. Pat. No. 5,817,705. This apparatus,commonly known as an “extruder-accumulator system” allows one to operatea process on an intermittent, rather than a continuous, basis. Theapparatus includes a holding zone or accumulator where foamable gelremains under conditions that preclude foaming. The holding zone isequipped with an outlet die that opens into a zone of lower pressure,such as the atmosphere. The die has an orifice that may be open orclosed, preferably by way of a gate that is external to the holdingzone. Operation of the gate does not affect the foamable compositionother than to allow it to flow through the die. Opening the gate andsubstantially concurrently applying mechanical pressure on the gel by amechanism (for example, a mechanical ram) forces the gel through the dieinto a zone of lower pressure. The mechanical pressure is sufficient toforce foamable gel through the die at a rate fast enough to precludesignificant foaming within the die yet slow enough to minimize andpreferably eliminate generation of irregularities in foamcross-sectional area or shape. As such, other than operatingintermittently, the process and its resulting products closely resemblethose made in a continuous extrusion process.

[0092] In the accumulating extrusion process, low density foamstructures having large lateral cross-sectional areas are preparedby: 1) forming under pressure a gel of the polymer or blend material anda blowing agent at a temperature at which the viscosity of the gel issufficient to retain the blowing agent when the gel is allowed toexpand; 2) extruding the gel into a holding zone maintained at atemperature and pressure which does not allow the gel to foam, theholding zone having an outlet die defining an orifice opening into azone of lower pressure at which the gel foams, and an openable gateclosing the die orifice; 3) periodically opening the gate; 4)substantially concurrently applying mechanical pressure by a movable ramon the gel to eject it from the holding zone through the die orificeinto the zone of lower pressure, at a rate greater than that at whichsubstantial foaming in the die orifice occurs and less than that atwhich substantial irregularities in cross-sectional area or shapeoccurs; and 5) permitting the ejected gel to expand unrestrained in atleast one dimension to produce the foam structure.

[0093] The present foam structures may also be formed into foam beadssuitable for molding into articles by expansion of pre-expanded beadscontaining a blowing agent. The beads may be molded at the time ofexpansion to form articles of various shapes. Processes for makingexpanded beads and molded expanded beam foam articles are described inPlastic Foams, Part II, Frisch and Saunders, pp. 544-585, Marcel Dekker,Inc. (1973) and Plastic Materials, Brydson, 5th ed., pp. 426-429,Butterworths (1989). Expandable and expanded beads can be made by abatch or by an extrusion process, and may be substantiallynon-crosslinked or substantially crosslinked.

[0094] The batch process of making expandable beads is similar tomanufacturing expandable polystyrene (EPS). The resulting foam structureis formed into non-crosslinked foam beads suitable for molding intoarticles. Discrete resin particles, such as granules made from theblends of the present invention, made either by melt blending orin-reactor blending, are impregnated with a blowing agent (andoptionally a cross-linking agent) in an aqueous suspension or in ananhydrous state in a pressure vessel at an elevated temperature andpressure. In the case of the aqueous supsension, the blowing agent (and,optionally, cross-linking agent) is/are introduced into the liquidmedium in which the granules are substantially insoluble (such as water)at an elevated pressure and temperature in an autoclave or otherpressure vessel. The granules are either discharged rapidly into anatmosphere or a region of reduced pressure to expand the granules intofoam beads or cooled and discharged as unexpanded beads. In a separatestep, the unexpanded beads are heated to expand them, for example, withsteam or with hot air. This process for making bead foams is well taughtin U.S. Pat. Nos. 4,379,859 and 4,464,484.

[0095] In a modification of the bead process, styrene monomer isoptionally impregnated into the suspended pellets of the blendcompositions of the present invention prior to their impregnation withblowing agent to form a graft interpolymer with the polymer material.The resulting interpolymer beads are cooled and discharged from thevessel substantially unexpanded. The beads are then expanded and moldedby an expanded polystyrene bead molding process within the skill in theart. Such a process of making such polyethylene/polystyrene interpolymerbeads is described for instance in U.S. Pat. No. 4,168,353.

[0096] A variation of the foregoing extrusion process readily yieldsexpandable thermoplastic polymer beads. The method tracks with theconventional foam extrusion process described above up to the dieorifice, which now contains one or multiple holes. The variationrequires (a) cooling the foamable gel to a temperature below that atwhich foaming occurs, (b) extruding cooled gel through a die containingone or more orifices to form a corresponding number of essentiallycontinuous expandable thermoplastic strands, (c) optionally quenchingthe strands exiting the die orifice in a cold water bath; and (d) andpelletizing the expandable thermoplastic strands to form expandablethermoplastic beads. Alternatively, the strands are converted to foambeads by cutting the strands into pellets or granules at the die faceand allowing the granules to expand.

[0097] The foam beads can also be prepared by preparing a mixture of thepolymer blend compositions of the present invention, cross-linkingagent, and chemical blowing agent in a suitable mixing device orextruder and form the mixture into pellets, and heat the pellets tocross-link and expand.

[0098] In another process for making cross-linked foam beads suitablefor molding into articles, the blends of this invention are melted andmixed with a physical blowing agent in a conventional foam extrusionapparatus to form an essentially continuous foam strand. The foam strandis granulated or pelletized to form foam beads. The foam beads are thencross-linked by radiation. The cross-linked foam beads may then becoalesced and molded to form various articles as described above for theother foam bead process. Additional teachings to this process are seenin U.S. Pat. No. 3,616,365 and C.P. Park, “Polyolefin Foam”, Handbook ofPolymer Foams and Technology, edited by D. Klempner and K. C. Frisch,Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), pp.224-228.

[0099] The foam beads may then be molded by any means known in the art,such as charging the foam beads to the mold, compressing the mold tocompress the beads, and heating the beads such as with steam to effectcoalescing and welding of the beads to form the article. Optionally, thebeads may be impregnated with air or other blowing agent at an elevatedpressure and temperature prior to charging to the mold. Further, thebeads may optionally be heated prior to charging. The foam beads areconveniently then molded to blocks or shaped articles by a suitablemolding method known in the art. Some of the methods are taught in U.S.Pat. Nos. 3,504,068 and 3,953,558. Excellent teachings of the aboveprocesses and molding methods are seen in C.P. Park, supra, p. 191, pp.197-198, and pp. 227-233, U.S. Pat. Nos. 3,886,100, U.S. Pat. Nos.3,959,189, U.S. Pat. Nos. 4,168,353 and U.S. Pat. Nos. 4,429,059.

[0100] The present crosslinked foam structure may also be made into acontinuous plank structure by an extrusion process utilizing a long-landdie as described in GB 2,145,961A. In that process, the polymer,chemical blowing agent and cross-linking agent are mixed in an extruder,heating the mixture to let the polymer cross-link and the blowing agentto decompose in a long-land die; and shaping and conducting away fromthe foam structure through the die with the foam structure and the diecontact lubricated by a proper lubrication material.

[0101] The present crosslinked foam structure may be made in bun stockform by two different processes. One process involves the use of across-linking agent and the other uses radiation.

[0102] The present crosslinked foam structure may be made in bun stockform by mixing the polymer compositions of this invention, across-linking agent, and a chemical blowing agent to form a slab,heating the mixture in a mold so the cross-linking agent can cross-linkthe polymer material and the blowing agent can decompose, and expandingby release of pressure in the mold. Optionally, the bun stock formedupon release of pressure may be re-heated to effect further expansion.

[0103] Foam may be made from cross-linked polymer sheet by eitherirradiating polymer sheet with high energy beam or by heating a polymersheet containing chemical cross-linking agent. The cross-linked polymersheet is cut into the desired shapes and impregnated with nitrogen in ahigher pressure at a temperature above the softening point of thepolymer; releasing the pressure effects nucleation of bubbles and someexpansion in the sheet. The sheet is re-heated at a lower pressure abovethe softening point, and the pressure is then released to allow foamexpansion.

[0104] Blowing agents useful in making the foam structures of thepresent invention include inorganic agents, organic blowing agents andchemical blowing agents. Suitable inorganic blowing agents includecarbon dioxide, nitrogen, argon, water, air, sulfur hexafluoride (SF₆)and helium. Organic blowing agents include aliphatic hydrocarbons having1-9 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fullyand partially halogenated aliphatic hydrocarbons having 1-4 carbonatoms. Aliphatic hydrocarbons include methane, ethane, propane,n-butane, isobutane, n-pentane, isopentane, neopentane. Aliphaticalcohols include methanol, ethanol, n-propanol, and isopropanol. Fullyand partially halogenated aliphatic hydrocarbons include fluorocarbons,chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbonsinclude methyl fluoride, perfluoromethane, ethyl fluoride,1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161),1,1,1-trifluoroethane (HFC-143 a), 1,1,1,2-tetrafluoroethane (HFC-134a),1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane,pentafluoroethane (HFC-125), difluoromethane (HFC-32), perfluoroethane,2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane,dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane.Partially halogenated chlorocarbons and chlorofluorocarbons for use inthis invention include methyl chloride, methylene chloride, ethylchloride, 1,1,1-trichloroethane, 1,1-dichloro-1 fluoroethane(HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b),chlorodifluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane(HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fullyhalogenated chlorofluorocarbons include trichloromonofluoromethane(CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane(CFC-113), dichlorotetrafluoroethane (CFC-114),chloroheptafluoropropane, and dichlorohexafluoropropane. Chemicalblowing agents include azodicarbonamide, azodiisobutyro-nitrile, bariumazodicarboxylate, N,N′-dimethyl-N,N′-dinitrosoterephthalamide, andbenzenesulfonhydrazide, 4,4-oxybenzene sulfonyl semicarbazide, andp-toluene sulfonyl semicarbazide, trihydrazino triazine and mixtures ofcitric acid and sodium bicarbonate such as the various products soldunder the name Hydrocerol™ (a product of Boehringer Ingelheim). Any ofthe foregoing blowing agents may be used singly or in combination withone or more other blowing agents. Preferred blowing agents includeisobutane, carbon dioxide, HFC-152a, and mixtures of the foregoing.

[0105] The amount of blowing agent incorporated into the polymer meltmaterial to make a foam-forming polymer gel is from 0.05 to 5.0,preferably from 0.2 to 3.0, and most preferably from 0.5 to 2.5 grammoles per kilogram of polymer.

[0106] Foams are optionally perforated to enhance or accelerate gaseouspermeation exchange wherein blowing agent exits from the foam and airenters into the foam. The resulting perforated foams have definedtherein a multiplicity of channels that are preferably free of directionwith respect to the longitudinal extension of the foam. The channelsextend from one foam surface at least partially through the foam, andsometimes completely through the foam from one external surface toanother external surface. The channels are advantageously present oversubstantially an entire exterior foam surface, preferably with uniformor substantially uniform spacing. Suitable spacing intervals may be upto and including 2.5 centimeters (cm), preferably up to and including1.3 cm. The foams optionally employ a stability control agent of thetype described above in combination with perforation to allowaccelerated permeation or release of blowing agent while maintaining adimensionally stable foam. U.S. Pat. Nos. 5,424,016,. U.S. Pat. Nos.5,585,058, WO 92/19439 and WO 97/22455, provide excellent informationrelative to perforation. If desired, the foams of this invention may bepost-treated by any known means to increase foam open cell content. Suchpost-treatment methods include, without limit, mechanically compressingthe foam and expanding the foam by exposure to steam and/or hot air.

[0107] Foams of the present invention generally have a density less than900, preferably less than 850, more preferably less than 800 kg/m³, evenmore preferably from 5 to 700 kilograms per cubic meter, and mostpreferably from 5 to 200 kilograms per cubic meter (in accordance withASTM D3575-93, Suffix W, Method B). The foams may be microcellular(i.e., with a cell size from less than about 0.05 mm, preferably fromabout 0.001 mm, to about 0.05 mm) or macrocellular (i.e., cell size ofabout 0.05 mm or more). The macrocellular foam has an average cell sizeof about 0.05 to about 15, preferably from about 0.1 to about 10.0, andmore preferably from about 0.1 to about 5 millimeters, preferably fromabout 0.2 to about 3 millimeters, and more preferably about 0.2 to about2 millimeters as measured according to the procedures of ASTM D3576-77.The preferred ranges of density and cell size should not be taken aslimiting the scope of this invention.

[0108] Foams of the present invention preferably exhibit excellentdimensional stability. Preferred foams retain 80 or more percent oftheir initial volume when measured one month after an initial volumemeasurement within 30 seconds after foam expansion. Volume is measuredby any suitable method such as cubic displacement of water.

[0109] The foams of the present invention have an open cell content thatranges from 0 to 100 volume percent based on the total volume of foam,as measured according to ASTM D2856-94, depending upon componentselection and process condition variations. Foams with an open cellcontent of 30 vol percent or less generally fall in a class known asclosed cell foams. Those known as open cell foams typically have an opencell content greater than 30, preferably greater than 40, and morepreferably greater than 50 vol percent. The open cell content isdesirably 100 vol percent or less, preferably 95 vol percent or less,and more preferably 90 vol percent or less.

[0110] The foams of density less than 100 kg/m³ generally have anAsker-C hardness of ≦90, desirably ≦80, and preferably ≦70. Hardnessmeasurements of the foams use an Asker C durometer for cellular rubberand yam in accordance with ASTM D2240-97, using a 5 mm diameterspherical indentor.

[0111] If the foam is in the shape of a sheet or plank, it has athickness that is generally ≧0.5 mm, preferably ≧1 mm and a width thatis generally ≧5 mm, preferably ≧10 mm. As used herein “thickness” of afoam plank or sheet refers to its smallest cross-sectional dimension(for example, as measured from one planar surface to an opposing planarsurface). When the foam is present as a round or rod, it has a diameterthat is generally ≧5 mm, preferably ≧10 mm.

[0112] The foam has a drop-test optimum C-factor (ASTM-D1596) of ≦6,desirably ≦5, and preferably ≦4.

[0113] Various additives may optionally be incorporated into thecompositions or foams of the present invention. The additives include,without limitation, stability control agents, nucleating agents,inorganic fillers, conductive fillers, pigments, colorants,antioxidants, acid scavengers, ultraviolet absorbers or stabilizers,flame retardants, processing aids, extrusion aids, anti-static agents,cling additives (for example, polyiso-butylene), antiblock additives,other thermoplastic polymers. Certain of the additives, such asinorganic and conductive fillers, may also function as nucleating agentsand/or open cell promoters for foams. Examples of antioxidants arehindered phenols (such as, for example, Irganox™ 1010) and phosphites(for example, Irgafos™ 168) both trademarks of, and commerciallyavailable from, Ciba Geigy Corporation.

[0114] The additives are advantageously employed in functionallyequivalent amounts known to those skilled in the art. For example, theamount of antioxidant employed is that amount which prevents the polymeror polymer blend from undergoing oxidation at the temperatures andenvironment employed during storage and ultimate use of the polymers.Such amount of antioxidants is usually in the range of from 0.01 to 10,preferably from 0.02 to 5, more preferably from 0.03 to 2 percent byweight based upon the weight of the polymer or polymer blend. Similarly,the amounts of any of the other enumerated additives are thefunctionally equivalent amounts.

[0115] A nucleating agent is optionally added to control the size offoam cells. Preferred nucleating agents include inorganic substancessuch as calcium carbonate, talc, clay, titanium dioxide, silica, bariumstearate, calcium stearate, diatomaceous earth, mixtures of citric acidand sodium bicarbonate, and the like. When used, the amount ofnucleating agent employed advantageously ranges from about 0.01 to about5 parts by weight per hundred parts by weight of a polymer resin.

[0116] In the manufacture of foams, a stability control agent (alsoknown as permeability modifier) is optionally added to the present foamto enhance dimensional stability. Preferred agents include amides andesters of C10-24 fatty acids. Such agents are seen in U.S. Pat. Nos.3,644,230 and 4,214,054. Esters may also reduce static during and afterfoam manufacture. Most preferred agents include stearyl stearamide,glyceromonostearate, glycerol monobehenate, and sorbitol monostearate.When used, such stability control agents are typically employed in anamount ranging from >0 to about 10 parts per hundred parts of thepolymer.

[0117] The foams of the present invention may be used in any applicationwhere foams of comparable density and open or closed cell contents areused today. Such applications include, without limit, cushion packaging(for example, corner blocks, braces, saddles, pouches, bags, envelopes,overwraps, interleafing, encapsulation) of finished electronic goodssuch as computers, televisions, and kitchen appliances; packaging orprotection of explosive materials or devices; material handling (trays,tote boxes, box liners, tote box inserts and dividers, shunt, stuffing,boards, parts spacers and parts separators); work station accessories(aprons, table and bench top covers, floor mats, seat cushions);automotive (headliners, impact absorption in bumpers or doors, carpetunderlayment, sound insulation); flotation (for example, life jackets,vests and belts); sports and leisure or athletic and recreationalproducts (for example, gym mats and bodyboards); egg cartons, meattrays, fruit trays, thermal insulation (such as that used in buildingand construction for wall sheathing, roofing, foundation insulation andresiding underlayment); acoustical insulation (for example, forappliances and building and construction); pipe insulation, insulationfor refrigeration, buoyancy applications (e.g., floatintg docks andrafts), floral and craft products, pallets, luggage liners, desk pads,footwear (including shoe soles), insulation blankets for greenhouses,case inserts, display foams, gaskets, grommets, seals; sound attenuationfor printers and typewriters; display case insert; missile containerpadding; military shell holder; blocking and bracing of various items intransport; preservation and packaging; automotives anti-rattle pads,seals; medical devices, skin contact pads; cushioned pallet; andvibration isolation pad. The foregoing list merely illustrates a numberof suitable applications. Skilled artisans can readily envisionadditional applications without departing from the scope or spirit ofthe present invention.

[0118] In another aspect, the polymer compositions of this invention maybe used to make foamed films. The film of the present invention may be amonolayer or a multilayer film. One or more layers of the film may beoriented or foamed. A multi-layer film of the present invention maycontain one, two or more layers comprising a blend as defined herein. Inone embodiment, the film according to the invention has a thickness of0.5 to 100 mils. Preferably, the present invention pertains to a toughand stiff film, comprising the blends of this invention. The film of theinvention may be printed. The film of the invention is obtainableaccording to methods known in the art. The film may be made using ablown or a cast film extrusion process, including co-extrusion andextrusion coating. One or more layers of the film may be expanded, forexample with a conventional blowing agent, to make foamed film. One ormore films may be laminated to form a multi-layer structure. Preferredare two-layer or three-layer films with one or two surface layers andthe foamed layer being the core layer. The surface layers may or may notcomprise the blends of this invention. In a three layer structure,preferably, the foamed layer is the core or middle layer. The films maybe (further) oriented after forming via tenter frame, double-bubble orother blown film techniques.

[0119] Foamed film is especially suitable for use as label or inthermoformable articles of manufacture. To make foamed film structures,either physical or chemical blowing agents may be used. A multilayerfilm of the invention comprising one or more foamed layers comprisingthe polymer compositions as defined herein is obtainable according tomethods known in the art, for example, using a co-extrusion process.

[0120] The label film may be constructed from printed, slit to width,rolls of film with the labels glued to a container, for example abottle, using conventional adhesives and glues known to the industry. Inaddition, the films of this invention may be printed, coated withpressure sensitive adhesives, laminated to release papers or films andapplied to bottles, containers or other surfaces by conventionalpressure sensitive techniques. The bottle may be a glass bottle or a PETbottle. Covering or affixed to a glass bottle, the label may also servea protective purpose. If the bottle is a PET bottle, the preferred labelis a wrap-around label.

[0121] The foregoing list merely illustrates a number of suitableapplications. Skilled artisans can readily envision additionalapplications without departing from the scope or spirit of the presentinvention.

[0122] The following examples are illustrative of the invention, but arenot to be construed as to limiting the scope thereof in any manner.

EXAMPLES

[0123] Blend Components Used in These Studies

[0124] HDPE 05862N is a high density polyethylene (a product of The DowChemical Company) having a nominal melt index (I2) of 5 g/10 min and anominal density of 0.9625 g/cm³.

[0125] HDPE 10462N is a high density polyethylene (a product of The DowChemical Company) having a nominal melt index (I2) of 10 g/10 min and anominal density of 0.9625 g/cm³.

[0126] AFFINITY™ SM1300 (a product and trademark of The Dow ChemicalCompany) has a nominal melt index (I2) of 30 g/10 min and a nominaldensity of 0.9020 g/cm³.

[0127] AFFINITY™ PL1280 (a product and trademark of The Dow ChemicalCompany) has a nominal melt index (I2) of 6 g/10 min and a nominaldensity of 0.9000 g/cm³.

[0128] DSV 10305.00 is a high density polyethylene (a product of The DowChemical Company) having a nominal melt index (12) of 1.1 g/10 min and anominal density of 0.9570 g/cm³.

[0129] LDPE 662i is a low density polyethylene (a product of The DowChemical Company) having a nominal melt index (12) of 0.5 g/10 min and anominal density of 0.9190 g/cm³.

[0130] LDPE 620i is a low density polyethylene (a product of The DowChemical Company) having a nominal melt index (12) of 1.8 g/10 min and anominal density of 0.9239 g/cm³.

[0131] LDPE 722 (a product of The Dow Chemical Company) has a nominalmelt index (I2) of 8 g/10 min and a nominal density of 0.9180 g/cm³.

[0132] LDPE 4012 (a product of The Dow Chemical Company) has a nominalmelt index (I2) of 12 g/10 min and a nominal density of 0.9180 g/cm³.

Examples 1-10 and Comparative Examples 1-6

[0133] Mixtures of high density polyethylene (HDPE) and low densitypolyethylene (LDPE) were dry blended and subsequently compounded on aLeistreitz 18 mm twin screw extruder with L/D=30 at 200 rpm. Thepolymers used were HDPE 05862N, HDPE 10462N and DSV10305.00 and LDPE662i. Example 1 also contained 0.4 weight percent mineral oil. The otherexamples and comparative examples did not contain mineral oil.Temperature settings were: Zone 1 −130° C.; zone 2 −170° C.; zone 3−190° C.; zone 4 −190° C.; zone 5 −190° C.; die −190° C. The melttemperatures ranged from 205° C. to 211° C. The data are presented inTable 1. The comparative examples were the individual polymers, orblends thereof, that were extruded at the same process settings, but didnot meet the criteria of the inventive examples.

[0134] The measured melt strength of the blends of the present inventionwas considerably greater than that predicted from a linear relationship.The melt strength ranged from 3.2 cN to 33.0 cN over a wide range ofmelt index (0.46 dg/min to 4.92 dg/min). These ranges of melt strengthand melt index are appropriate for making a variety of foams (differentdensities, different shapes and geometries, cross-linked,non-crosslinked, etc). The melt strength of the inventive blends wasgreater than that of HDPE of similar melt index (Comparative Example 1versus Example 1; Comparative Example 3 versus Examples 6-8). Theinventive blend of Example 10 exhibited similar melt strength as LDPE662i (Comparative Example 4), but the melt index of the blend was higherand its flexural modulus was significantly greater. The flexural modulusof the inventive blends was greater than 100,000 psi, and even as highas that of HDPE (Comparative Examples 1-3 versus Examples 1-3). Theupper service temperature of the inventive blends was greater than 120°C.

Examples 11-14 and Comparative Examples 7-8

[0135] Mixtures of HDPE 05862N and LDPE 620i were dry blended andsubsequently compounded on a Leistreitz 18 mm twin screw extruder withL/D =30 at 200 rpm. Temperature settings were: Zone 1 −130° C.; zone 2−170° C.; zone 3 −190° C.; zone 4 −190° C.; zone 5 −190° C.; die −190°C. Melt temperatures ranged from 204° C. to 211° C. The data arepresented in Table 2. The comparative examples were the blends that didnot meet the flexural modulus criterion of the inventive examples.

Examples 15-18 and Comparative Examples 9-18

[0136] Mixtures of AFFINITY™ SM1300 and various grades of LDPE were dryblended and subsequently compounded on a Leistreitz 18 mm twin screwextruder with L/D=30 at 100 rpm. Temperature settings were: Zone 1 −185°C.; zone 2 −185° C.; zone 3 −185° C.; zone 4 −185° C.; zone 5 −185° C.;die −185° C. The data are presented in Table 3. The comparative exampleswere the blends that did not meet one or more of the criterion of theinventive examples.

Examples 19-33

[0137] Mixtures of AFFINITY™ PL1280 and various grades of LDPE were dryblended and subsequently compounded on a Leistreitz 18 mm twin screwextruder with L/D=30 at 100 rpm. Temperature settings were: Zone 1 −185°C.; zone 2 −185° C.; zone 3 −185° C.; zone 4 −185° C.; zone 5 −185° C.;die −185° C. The data are presented in Table 4. TABLE 1 HDPE, LDPE andBlends Comprising LDPE 662i Melt Flex Wt % Wt % I2 Measured MeltPredicted Melt Extensibility Modulus UST Comp A A Comp B B (g/10 min)strength (cN) Strength (cN)* F_(MS) (mm/s) (psi) (° C.) Comp Ex 1 HDPE05862N 100 None 0 5.16 1.0 N/A N/A 250 232032 141.5 Comp Ex 2 HDPE10462N 100 None 0 8.61 0.7 N/A N/A 155 248627 143.3 Comp Ex 3DSV10305.00 100 None 0 1.11 4.3 N/A N/A 110 192315 133.6 Comp Ex 4 None0 LDPE 662i 100 0.32 33.5 N/A N/A 78  40202 113.7 Comp Ex 5 HDPE 05862N25 LDPE 662i 75 0.61 32.0 18.68 1.71 95  74191 127.4 Comp Ex 6 DSV10305.00 25 LDPE 662i 75 0.34 42.0 27.41 1.53 88  70856 133.7 Ex 1 HDPE10462N 80 LDPE 662i 20 4.92 7.7 2.15 3.58 380 195144 129.5 Ex 2 HDPE05862N 95 LDPE 662i 5 4.46 3.2 1.54 2.08 430 218739 143.4 Ex 3 HDPE05862N 90 LDPE 662i 10 4.16 5.2 1.87 2.78 350 210480 141.4 Ex 4 HDPE05862N 75 LDPE 662i 25 2.51 12.5 3.70 3.37 240 176754 139.3 Ex 5 HDPE05862N 65 LDPE 662i 35 1.93 17.5 5.27 3.32 160 160499 137.5 Ex 6 HDPE05862N 50 LDPE 662i 50 1.18 24.0 9.09 2.64 130 111942 135.1 Ex 7 DSV10305.00 95 LDPE 662i 5 0.96 7.5 4.17 1.80 110 166726 140.8 Ex 8 DSV10305.00 90 LDPE 662i 10 0.96 10.5 4.86 2.16 150 156802 140.7 Ex 9 DSV10305.00 75 LDPE 662i 25 0.63 20.0 9.14 2.19 155 136443 138.7 Ex 10 DSV10305.00 50 LDPE 662i 50 0.46 33.0 16.85 1.96 105 104505 124.9

[0138] TABLE 2 HDPE 05862N/LDPE 620i Blends Predicted Melt Strength (cN)Measured Calculated Melt from Linear Melt Flexural Wt % Wt % Index, I2Measured Melt Composition Extensibility Modulus Component A A ComponentB B (g/10 min) strength (cN) Model F_(MS) (mm/s) (psi) Comp Ex 7 HDPE05862N 20 LDPE 620i 80 1.39 19.5 11.4 1.71 218  78093 Comp Ex 8 HDPE05862N 10 LDPE 620i 90 1.30 20.0 13.1 1.53 176  64907 Ex 11 HDPE 05862N90 LDPE 620i 10 4.22 3.8 1.85 2.05 375 210740 Ex 12 HDPE 05862N 80 LDPE620i 20 3.92 6.6 2.49 2.65 449 189880 Ex 13 HDPE 05862N 60 LDPE 620i 402.45 11.9 4.89 2.44 265 147820 Ex 14 HDPE 05862N 35 LDPE 620i 65 1.7317.2 8.49 2.03 236 101366

[0139] TABLE 3 Blends of AFFINITY ™ SM1300 With LDPE Melt Calculated Wt% Wt % I2 Melt strength Predicted Melt Extensibility Flexural Comp A AComp B B (g/10 min) (cN) Strength (cN) F_(MS) (mm/s) Modulus (psi) CompEx 9 AFFINITY ™ SM1300 85 LDPE 620i 15 20.3 0 0.76 0.00 N/A 18095 CompEx 10 AFFINITY ™ SM1300 25 LDPE 620i 75 3.6 9.2 5.83 1.58 N/A 39379 CompEx 11 AFFINITY ™ SM1300 10 LDPE 620i 90 2.5 12 8.51 1.41 N/A 47486 CompEx 12 AFFINITY ™ SM1300 90 LDPE 662i 10 22 0.8 0.63 1.26 N/A 16893 CompEx 13 AFFINITY ™ SM1300 90 LDPE 722 10 27.6 0 0.55 0.00 N/A 16370 CompEx 14 AFFINITY ™ SM1300 80 LDPE 722 20 23.5 0.4 0.78 0.52 N/A 18095 CompEx 15 AFFINITY ™ SM1300 50 LDPE 722 50 15.4 1.4 1.69 0.83 N/A 24140 CompEx 16 AFFINITY ™ SM1300 40 LDPE 722 60 12.1 3.1 2.24 1.38 N/A 26567 CompEx 17 AFFINITY ™ SM1300 25 LDPE 722 75 11.3 4 2.75 1.45 N/A 30611 CompEx 18 AFFINITY ™ SM1300 15 LDPE 722 85 8.6 5.2 3.62 1.44 N/A 33781 Ex 15AFFINITY ™ SM1300 70 LDPE 620i 30 15.4 2.5 1.24 2.01 N/A 22176 Ex 16AFFINITY ™ SM1300 50 LDPE 620i 50 8.2 5.4 2.55 2.11 N/A 28697 Ex 17AFFINITY ™ SM1300 80 LDPE 662i 20 15 3 1.04 2.89 N/A 18208 Ex 18AFFINITY ™ SM1300 50 LDPE 662i 50 3.9 12.5 4.16 3.01 N/A 24580

[0140] TABLE 4 Blends Of AFFINITY ™ PL1280 With LDPE Melt Calculated Wt% Wt % I2 Melt strength Predicted Melt Extensibility Flexural Comp A AComp B B (g/10 min) (cN) Strength (cN) F_(MS) (mm/s) Modulus (psi) Ex 19AFFINITY ™ PL1280 90 LDPE 722 10 5.56 2.4 1.55 1.55 345 14609 Ex 20AFFINITY ™ PL1280 85 LDPE 722 15 5.24 3.0 1.84 1.63 315 15467 Ex 21AFFINITY ™ PL1280 80 LDPE 722 20 5.17 3.7 2.08 1.78 310 16268 Ex 22AFFINITY ™ PL1280 50 LDPE 722 50 5.66 6.2 3.26 1.90 395 22722 Ex 23AFFINITY ™ PL1280 40 LDPE 722 60 5.31 6.3 3.84 1.64 350 25329 Ex 24AFFINITY ™ PL1280 25 LDPE 722 75 6.35 6.8 4.02 1.69 365 29728 Ex 25AFFINITY ™ PL1280 90 LDPE 662i 10 4.02 4.2 1.91 2.20 265 14609 Ex 26AFFINITY ™ PL1280 85 LDPE 662i 15 3.50 6.2 2.39 2.59 380 15467 Ex 27AFFINITY ™ PL1280 80 LDPE 662i 20 3.29 7.3 2.80 2.61 300 16370 Ex 28AFFINITY ™ PL1280 50 LDPE 662i 50 1.44 16.4 7.98 2.06 160 23139 Ex 29AFFINITY ™ PL1280 90 LDPE 4012 10 5.64 2.1 1.54 1.37 305 14609 Ex 30AFFINITY ™ PL1280 85 LDPE 4012 15 5.80 2.5 1.72 1.45 300 15467 Ex 31AFFINITY ™ PL1280 80 LDPE 4012 20 5.88 2.6 1.91 1.36 230 16268 Ex 32AFFINITY ™ PL1280 50 LDPE 4012 50 6.64 4.0 2.93 1.36 205 22722 Ex 33AFFINITY ™ PL1280 25 LDPE 4012 75 8.26 5.2 3.38 1.54 380 29728

Examples 34-36 and Comparative Example 19

[0141] A mixture of high density polyethylene (HDPE) and LDPE was meltblended on a 40 mm twin screw extruder at 252 rpm and 175 lb/hr. Thetemperature profile in the extruder was: zone 2 −171° C.; zone 3 −190°C.; zone 4 −208° C.; zone 5 −218° C.; zone 6 −229° C.; zone 7 −241° C.;zone 8 −214° C.; zone 9 −224° C.; die −221° C. The final melttemperature was 285° C. The final properties of the blend are presentedin Table 5. This blend composition is intermediate between thecompositions of Examples 9 and 10 (Table 5). TABLE 5 Blend of LDPE andHDPE Melt Melt Melt Flex Blend I2 Density Tension Strength ExtensibilityModulus Composition (g/10 min) (g/cm³) (g) (cN) (mm/s) (psi) Ex 34 35weight 0.51 0.9423 10.5 25.4 130 122987 percent LDPE 662i 65 wt percentHDPE DSV10305.00

[0142] The blend of Example 34 was subsequently foamed using anextrusion foaming process with isobutane as blowing agent. ComparativeExample 19 was a conventional foam made from LDPE 662i. Glycerolmonostearate (GMS) was used as permeability modifier and talc asnucleator. The properties of the resulting foams are summarized in Table6. NOTE: “phr” corresponds to part-per-hundred resin. TABLE 6 Foam fromBlend of LDPE and HDPE Foam 3D Av Normalized Density Cell CompressiveStrength (kg/m³) − Open Cells Size (psi/pcf) @ ASTM (volume (mm)5/10/25/50/75% D3575- percent) − (foam Deflection ASTM Polymer Talc GMSIsobutane 93 Suffix ASTM age 7 D3575-93 Suffix D Composition (phr) (phr)(phr) W D2856-87 Days) (foam age 28 Days) Comp Ex LDPE 662i 0.5 0.3 1230.0 71 1.93 0.8/2.5/3.4/4.2/10.0 19 Ex 35 Blend Of Ex 0.13 0.3 10 34.089 1.12 1.9/6.6/8.7/11.0/28.6 34 Ex 36 Blend Of Ex 0.13 0.3 15 26.8 550.82 1.7/6.0/10.8/20.0/49.5 34

[0143] Foams of density ranging from about 27 kg/m³ to about 34 kg/m³were successfully made from the blend of Example 34. Open cells could bevaried from 55 to 89 vol percent. The cell sizes of the foams rangedfrom about 0.8 to about 1.1 mm. The Normalized Compressive Strengths(Total Compressive Strength/Density) of the foams of Example 35 and 36were significantly greater than that of the reference foam (ComparativeExample 19), even at lower foam density. These data indicate that foamsmade from the blends of this invention (Examples 34-36) exhibitsignificantly higher load bearing capability relative to foams made fromLDPE alone, at similar densities and open cell contents. Or, foams madefrom the blends of this invention (Examples 34-36) will have equivalentload bearing capability to LDPE foams, but at comparatively lower foamdensity

What is claimed is:
 1. A blend which comprises; A) a heterogeneous orhomogenous linear ethylene homopolymer or interpolymer and B) a branchedhomopolymer or interpolymer; wherein said blend has; 1) a melt index,I2, of about 0.05 to about 20 g/10 min; 2) a flexural modulus of≧100,000 psi; 3) a melt strength of ≧2 cN; 4) a melt extensibility of≧25 mm/sec; 5) a UST greater than about 115° C.; and 6) wherein saidmelt strength of said blend meets the following relationship; Meltstrength≧F _(MS)* [(f*A)+((1−f)*B)] where A=3.3814*(I2)^(−0.6476) andB=16.882*(I2)^(−0.6564); I2 is the measured melt index of the blend; fis the weight fraction of the linear component in the blend, and F_(MS)is ≧1.1.
 2. The blend of claim 1 wherein A) Component A has a meltindex, I2, of less than about 60 g/10 min and is a heterogeneous orhomogenous linear ethylene homopolymer, or a heterogeneous or homogenouslinear interpolymer of ethylene with at least one C₃-C₂₀ α-olefin; andB) Component B is selected from the group consisting of LDPE, EVA, andEAA; and wherein said blend has; 1) a melt index, I2, of about 0.1 toabout 10 g/10 min; 2) a flexural modulus of ≧120,000 psi; 3) a meltstrength of ≧7 cN; 4) a melt extensibility of ≧50 mm/sec; 5) a USTgreater than about 118° C.; and 6) F_(MS) is ≧1.25.
 3. The blend ofclaim 1 wherein A) Component A has a melt index, I2, of less than about30 g/10 min and is a linear or substantially linear ethylene homopolymeror a linear or substantially linear ethylene/C₃-C₈ α-olefininterpolymer, and B) Component B is LDPE; and wherein said blend has; 1)a melt index, I2, of about 0.2 to about 7 g/10 min; 2) a flexuralmodulus of ≧130,000 psi 3) a melt strength of ≧10 cN; 4) a meltextensibility of ≧75 mm/sec; 5) a UST greater than about 121° C.; and 6)F_(MS) is ≧1.5.
 4. The blend of claim 3 wherein Component A has a meltindex, I2, of less than about 15 g/10 min, and wherein said blendhas; 1) a melt index, I2, of about 0.5 to about 5 g/10 min; 2) a USTgreater than about 125° C.; and 3) F_(MS) is ≧2.5.
 5. A blend whichcomprises; A) a heterogeneous or homogenous linear ethylene homopolymeror interpolymer; B) a branched homopolymer or interpolymer; wherein saidblend has; 1) a melt index, I2, of about 0.05 to about 20 g/10 min; 2) aflexural modulus of ≦30,000 psi; 3) a melt strength of ≧2 cN; 4) a meltextensibility of ≧25 mm/sec; and 5) wherein said melt strength of saidblend meets the following relationship; Melt strength≧F _(MS)*[(f*A)+((1−f)*B)]; where: A=3.3814*(I2)^(−0.6476) andB=16.882*(I2)^(−0.6564); where I2 is the measured melt index of theblend; f is the weight fraction of the linear polyethylene in the blendand F_(MS) is ≧1.1.
 6. The blend of claim 5 wherein A) Component A has amelt index, I2, of less than about 60 g/10 min and is a heterogeneous orhomogenous linear ethylene homopolymer or heterogeneous or homogenouslinear interpolymer of ethylene with at least one C₃-C₂₀ α-olefin, andB) Component B is selected from the group consisting of LDPE, EVA, andEAA; and wherein said blend has; 1) a melt index, I2, of about 0.1 toabout 10 g/10 min; 2) a flexural modulus of ≦25,000psi; 3) a meltstrength of ≧7 cN; 4) a melt extensibility of ≧50 mm/sec; and 5) F_(MS)is ≧1.25.
 7. The blend of claim 5 wherein A) Component A has a meltindex, I2, of less than about 30 g/10 mins, and is a linear orsubstantially linear ethylene homopolymer or a linear or substantiallylinear ethylene/C₃-C₈ α-olefin interpolymer; and B) Component B is LDPE;wherein said blend has; 1) a melt index, I2, of about 0.2 to about 7g/10 min; 2) a flexural modulus of ≦20,000 psi 3) a melt strength of ≧10cN; 4) a melt extensibility of ≧75 mm/sec; and 5) F_(MS) is ≧1.5.
 8. Theblend of claim 7 wherein Component A has a melt index, I2, of less thanabout 15 g/10 min, and wherein said blend has; 1) a melt index, I2, ofabout 0.5 to about 5 g/10 min; and 2) F_(MS) is ≧2.5.
 9. A blendcomprising the blend of claim 1 or claim 5, further comprising one ormore additional polymers selected from the group consisting of lowdensity polyethylene, high density polyethylene (HDPE), linear lowdensity polyethylene (LLDPE), ethylene styrene interpolymers (ESI),polypropylene (PP), polystyrene (PS), ethylene-propylene rubber andstyrene-butadiene rubber.
 10. A foam comprising the blend of claim 9,said foam being either; 1) substantially uncrosslinked, having a gelcontent of 50 or less weight percent gel based upon the total weight offoam, as measured according to ASTM D-2765-84, Method A; or 2)substantially cross-linked, having a gel content of greater than 50weight percent gel based upon the total weight of foam, as measuredaccording to ASTM D-2765-84 Method A.
 11. A film, fiber, blow-moldedarticle, wire and cable article or extrusion coating made from the blendof claims 1 or
 5. 12. A process for making either a substantiallyuncrosslinked foam having a gel content of 50 or less weight percentbased upon the total weight of foam (as measured according to ASTMD-2765-84, Method A); or a substantially cross-linked foam having a gelcontent of greater than 50 weight percent based upon the total weight offoam (as measured according to ASTM D-2765-84 Method A), from the blendof claims 1, 5 or 9.